Light Curtains - Insights

Results of a Poll of IHS Engineering360 subscribers

How to Select Light Curtains
Image credit: Keyence; OSHA; Machine Guard Solutions
Light curtains are presence sensing devices that provide an infrared perimeter around perilous machinery or processes. When an infrared beam is interrupted between the transmitter and receiver, a killswitch arrests the hazard until the optical boundary has been reestablished.
Light Curtain Operation
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Q & A on Light Curtains

We asked our users for their input on Light Curtains.
Here are the results of 112 users
familiar with Light Curtains.

Being able to use muting, fixed and floating blanking in a standard priced light curtain so the customer who does not need those features will not need to pay for them, but in the future if the need arises, not have to change to a different type of light curtain. Also, having the ability to expand either in size or using multiple light curtains in series and not be concerned with the increase in response time that would cause a redesign to add distance to pinch point.

~Charles S, Product Manager, Wanaque, NJ

Led and photodiode technology. Specific ASIC that reduces part count, cost and reliability. Efficiencies in optic design and the use of redundant microprocessors.

~James L, unemployed, Bend, OR

User friendly for the operators with a range of control options, systems that are easy to trouble shoot, and parts accessibility.

~Manufacturing, Timmins, Canada

Stronger housing design to enhance the PCB and Light curtain work properly when used in press high speed shock.

~Stanley P, Marketing/Sales, Taiwan, R.O.C.

Integrated monitoring and control to reduce the cost and space requirements of external monitoring modules.

~Larry K, Project Manager, Benton Harbor, MI

Cost, ease of use, availability of multiple use for the same model, compatibility with existing equipment.

From your perspective, which companies are creating the most innovative light curtains?

15 answers

Answers:

There are a number of good products available. Keyence has a good compact design where space is an issue. Banner has also released a smaller form factor light curtain now. Banner's documentation has a lot of information included in it although I find it a little difficult to navigate and interpret at times. Banner has an excellent safety division application and tech support group that offsets any challenges in understanding their documentation.

~Larry K, Project Manager, Benton Harbor, MI

Panasonic/Sunx has developed different types of light curtains for all types of applications. The SF4B series uses muting, fixed and floating blanking with a 14ms response time regardless of size and up to 3 light curtains in series. The SF4C is the newest low profile light curtain with a 13mm wide area. Also the ST4 is individual thru beams that can be used for all sorts of applications.

~Charles S, Product Manager, Wanaque, NJ

Keyence - high speed output Schmersal - Light guard with possibility to have fixed and floating blanking plus muting all at the same time. Sick -

~Conrad S, Marketing/Sales, CANNOCK, UK

Most specialist companies do a decent curtain, my personal choice (I am a distributor) is Smartscan.

All sorts of applications, from basic guarding to using muting to allow parts to pass through the light curtain and maintain an active status to the machine.

~Charles S, Product Manager, Wanaque, NJ

My most typical use is to guard the opening of a machine where the machine operator needs to reach into a machine's danger zone to remove and/or place the parts being machined or trimmed. Using a type 4 light curtain, we can allow the machine operator to enter the danger zone of the machine to remove and replace the parts as required. Once the parts are in place, the light curtain verifies that the plane of the light curtain is clear, and by the design of the machine we know that there is no way possible for the machine operator to be inside the machine's danger zone. The result is that the proper arrangement of controls can then allow a machine to be initiated with a single operator input and allows the machine operator to be free to do other work while the machine is in its cycle rather than tying both of the operators' hands down to a two hand safety logic circuit for the entire machine cycle.

Please share with us any “non-standard” applications that a light curtain has been used for.

10 answers

Answers:

I have applied a light curtain on the opening to a machine that is integrated in a robotic production cell where the safety standards are satisfied at the perimeter of the cell and the machinery is not attended by a warm body. We did not need the safety rated (Human Operator) functionality but did use the light curtain in a similar fashion for machine safety. It was determined that the expense to use a light curtain to protect the tooling on the pick and place robot was a cost effective insurance way to improve operating reliability and efficiency.

~Larry K, Project Manager, Benton Harbor, MI

Mount on top of elevators to detect if any person was on car to prevent the car from continuing its travel if there is an engineer on the top or someone is "surfing" the lift shaft.

~Conrad S, Marketing/Sales, CANNOCK, UK

Equipment Protection. With Safety Light Curtains you have a known failure mode (i.e. OFF) that you can design your application around, such as non-contact motion limiting.

~Mike C, Safety Product Manager, Minneapolis, MN

We have an in house process which needed operator protection. I purchased a 6 in.high light curtain with a 12 in. protection length needed.

Do you know of any disastrous mistakes that occurred due to the incorrect usage of a light curtain?

7 answers

Answers:

I have seen an application where the electrical controls were safe in operating sequence but not the physical machine. It is critical that the correct combination of ALL components is found to achieve a safe machine. ALL power must be removed from components that cause motion to reach a safe state. Closed center valves for pneumatic and/or hydraulic power, dump valves for pneumatic and/or hydraulic accumulators, mechanical brakes on motors, and other items must ALL be taken into account to insure that the machine will be stopped in a safe condition upon opening the safety circuit.

~Larry K, Project Manager, Benton Harbor, MI

Mounting the sensing field too close to the hazard (e.g. < 4") will many times lead to an injury.

~Mike C, Safety Product Manager, Minneapolis, MN

Yes. The light curtain was interfaced to a non safety relay and the interface relay contacts failed in an unsafe mode not stopping the machine. An override switch was installed with out lock out tag out and or key interface. Applying a light curtain on a full revolution press.

~James L, unemployed, Bend, OR

Engineers designing in the wrong resolution for a dangerous machine and also calculating the wrong stopping distance.

It would be nice to have the "Mute" functionality built into the curtain as a standard option.

~Larry K, Project Manager, Benton Harbor, MI

Good documentation. I have had sales people from several vendors tell me how great their product is, only to dig into the documentation and find it's very weak or non existent. That will make first time users (like me) or infrequent users call tech support for something that should be in the manuals.

~Joe A, Engineer, St. Louis, MO

Wireless output system which would allow just a 2 or 3 wire connection for supply only.

~Conrad S, Marketing/Sales, CANNOCK, UK

Simple inbuilt muting. Ease of alignment. Easy visual indication of set up and faults.

~Marketing/Sales, milton keynes, Great Britain

Reliable, cost effective, easy to use, short lead times, good customer service.

Is there any advice you want to share with users to help them avoid common errors in selection or usage of a light curtain?

12 answers

Answers:

The most common error is mounting too close to the danger zone of the machine because of errors in calculation of stop time of the machinery. Make sure the interface to the light curtain is fail safe and circuits connected to properly shut down machinery in case of a failure. Make sure the light curtain is sized correctly so an operator can not reach under or over. It may require mechanical guarding along with the light curtain. Pay attention to the machine environment, shock, vibration, oil water etc.

~James L, unemployed, Bend, OR

Some customers think finger type safety light curtains are needed for all applications. Use the safety distance calculation formula to determine the best minimum detection spacing required for your application. In some instances a hand type safety light curtain with a fast response can be used in place of a more expensive finger type safety light curtain.

~Charles S, Product Manager, Wanaque, NJ

Don't pretend you know what you are doing if you don't! Read the selection guides and if you don't know ASK. It is very difficult to get any technical support on light curtains due to their safety status aka "potential lawsuit". But I have experienced many errors in application that are just due to ignorance or lack of reading the included documentation.

~Joe A, Engineer, St. Louis, MO

Compatibility with equipment/ machines already in use. Need to pay attention to space, voltage, operator positioning and the like. Also be sure you need a light curtain. We have purchased light curtains not needed.

~Dick M, Technical Support, Newport, NH

For Safety: Define correct resolution and protective height which suits the application. For this knowledge of standards (ANSI B11.19) and ISO 13855 is necessary.

~Juergen B, Edina, MN

1) Buying a high resolution / detection capability 14mm system when a lower cost 30mm system will do the job.
2) Read and follow the manuals that are provided.

Do you have any advice for people relative to buying or using light curtains?

12 answers

Answers:

If you are faced with your first application of a light curtain in the safety circuit of a machine it is well worth your time to call Banner and talk to their application engineers about your application. They will take all the time you need to solve your application needs with the simplest possible combination to meet the required safety standards.

~Larry K, Project Manager, Benton Harbor, MI

1. Make sure they are mounted correctly according to applicable standards, measure stopping time of machine, make sure your interface to stop the inertia of the machine is failsafe and control reliable, the manufacturer you choose must have a reliable product, investigate MTBF, hire a professional to guide you through the proper installation.

~James L, unemployed, Bend, OR

Buyer Beware !!! There is a lot of intentional misinformation to cause confusion. Find a reputable manufacturer. Watch out for anyone trying to sell a "finger protection" or "hand protection" system. A properly mounted sensing field, no matter what the resolution / detection capability will "protect" all parts of the body equally.

~Mike C, Safety Product Manager, Minneapolis, MN

Buy in the country of use when possible, local backup is important. Many regulations make it illegal to tamper with safety devices unless you are a certified manufacturer.

~Jim P, Engineering Consultant, Derby, United Kingdom

Select a light curtain that is versatile enough to fill the needs of your application today, but also has the features that you will maybe need in future machine redesigns.

~Charles S, Product Manager, Wanaque, NJ

All light guards are the same but be aware of the ones that require a shielding connection as EMC will affect them.

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